1. Field of the Invention
The present invention relates to a low cost manufacturing technique to produce composite linear motion bearing structures. More particularly, this method of manufacturing greatly simplifies the fabrication of the bearing rail while facilitating efficient and inexpensive production.
2. Description of Related Art
Linear motion bearing assemblies are well known in the art and are employed to move machine and machine tools and other equipment with respect to each other. These bearing assemblies typically include rail and carriage structures, rolling elements, and provisions for recirculation and lubrication. See, for example, U.S. Pat. No. 4,932,067 to Pester et al. Typically, these bearings are manufactured from monolithic structures comprised of high quality bearing steels. The sequence of manufacture of the rail and carriage for this type of bearing assemblies is typically, cold drawing, machining, heat treating and grinding. The processing is generally performed on elaborate and expensive machining equipment, leading to substantial cost. In addition, one characteristic of high quality bearing steel is its rigidity. This characteristic results in a requirement for extreme precision in grinding the load bearing tracks and highly accurate installation of the linear motion bearing assembly to avoid overly stressing the contact portions.
Attempts have been made in the past to reduce the amount of bearing steel that requires processing by applying the high quality bearing steel only in the contact areas. See, for example, U.S. Pat. Nos. 3,900,233 and 4,025,955 to Thompson; and U.S. Pat. Nos. 4,515,413, 4,527,841, 4,531,788 and 4,576,421 to Teramachi. A variety of techniques are provided for attaching the bearing steel insert to the supporting body. The techniques include press fitting, mating of dove tails, cold forming of the bearing steel insert and cold forming of the support structure.
Attempts have also been made in the past to improve positioning of the bearing steel in the supporting body. For example, U.S. Pat. No. 4,576,420 to Lehman, discloses utilization of the preload of the rolling elements to position the bearing steel in the carriage. U.S. Pat. No. 4,774,247 to Isert discloses usage of integral clamping force afforded by the support structure to hold the bearing steel. U.S. Pat. No. 5,067,823 to Kasuga discloses a plastically deforming process of the support structure through roll forming. U.S. Pat. No. 5,059,037 to Albert and U.S. Pat. No. 5,161,896 to Hofling disclose floating of the bearing steel insert until it is positioned by the reaction of the rolling element. U.S. Pat. No. 5,217,308 to Schroeder discloses attachment of the bearing steel by mating surfaces or thorough press fit.
Therefore, it would be highly desirable to eliminate or reduce the expensive materials and the requirements of each of these manufacturing steps. At the very least, it would be desirable to emphasize the inexpensive materials and steps and de-emphasize the expensive materials and steps.
Accordingly, it is an object of the present invention to provide an efficient and simplified manufacturing process which minimizes the cost related to fabrication of the bearing rail and attachment of the bearing steel insert while providing the capability of optimizing the quality of manufactured linear motion bearing assembly.
Objects and advantages of the invention are set forth in part herein and in part will be obvious therefrom, or may be learned by practice with the invention, which is realized and attained by means of the instrumentalities and combinations pointed out in the appended claims. The invention consists of novel parts, constructions, arrangements, combinations, steps and improvements herein shown and described.